Traumatic injuries and deaths resulting from slip and fall accidents are a significant public health problem in the United States. The economic loss due to lost employment time is an important factor in many industrial settings and the likelihood of injuries resulting from slip and fall accidents is an increasing concern in general, particularly as the population ages. Numerous measures have been undertaken in an attempt to reduce the number of slip and fall accidents including, but not limited to, the use of slip resistant materials on walkway surfaces and prescribed shoe outsole materials and patterns. Various factors known to influence the likelihood of a macroslip have been quantified/ranked by numerous investigators.
The classical notion of Coulomb friction has traditionally been applied to the analysis of slip and fall accidents in an oversimplified manner despite its known and acknowledged shortcomings. For hard, rigid material surfaces in contact, Coulomb demonstrated that the magnitude of the friction force, F, acting on the contact surfaces in opposition to relative motion between the surfaces is proportional to the magnitude of the normal force, N. However, the constant of proportionality, μ, differs with the state of motion. As is well-known by those of ordinary skill, μ can be viewed as the coefficient of friction or as a slip resistance measurement, a parameter that can be measured with, for example, a tribometer. For impending slip just at, or immediately prior to, relative motion between the surfaces, the magnitude of the friction force, F=μsN, and for contact surfaces in relative motion, the magnitude of the friction force, F=μkN, where μs is the coefficient of static friction and μk is the coefficient of kinetic (dynamic) friction. Typically, μs is higher than μk. In addition, μs and μk are dependent upon both materials in contact.
In Coulomb friction theory, the friction force is independent of both the contact area and the relative speed of the materials in contact once relative motion of the surfaces has commenced. For compliant (deformable) materials in contact, such as shoe outsole and flooring materials, these are simplifying assumptions which may not lead to an appropriate model in many circumstances. The onset of slip is a function of many factors, and the probability of a slip occurring cannot typically be based on a single quantity, or parameter, such as the coefficient of friction alone. For instance, several individuals can walk across the same surface, wearing substantially similar footwear, and some may slip while others negotiate the walkway with no trouble.
Therefore, a need exists for an improved system and method for determining macroslip.